Most look at ageing as a process from young and healthy to becoming weaker with age until we die. However, new studies have found an incredible diversity within the ageing process of various species.

Not all species weaken and become more likely to die as they age. In fact, some get stronger and less likely to die, while others are unaffected by age.

The study covered different species of mammals, vertebrates, invertebrates, plants and algae to find a surprising diversity of mortality conditions and ageing processes.

The desert tortoise (Gopherus agassizii) experiences the highest mortality early in life and a steadily declining mortality as it ages. Many plant species (such as the white mangrove tree (Avicennia marina)) also follow this decreasing mortality pattern.

There are also species that have constant mortality and remain unaffected by the aging process. This is most striking in the freshwater polyp Hydra magnipapillata which has constant low mortality. In fact, in lab conditions, it has such a low risk of dying at any time in its life that it is effectively immortal.